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    Subject[PATCH RT 20/25][RFC 3.0.23-rt39-rc1] futex/rt: Fix possible lockup when taking pi_lock in proxy handler
    From: Steven Rostedt <rostedt@goodmis.org>

    When taking the pi_lock, we must disable interrupts because the
    pi_lock can also be taken in an interrupt handler.

    Use raw_spin_lock_irq() instead of raw_spin_lock().

    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    Cc: Carsten Emde <C.Emde@osadl.org>
    Cc: John Kacur <jkacur@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Clark Williams <clark.williams@gmail.com>
    Cc: stable-rt@vger.kernel.org
    Link: http://lkml.kernel.org/r/20120301190345.165160680@goodmis.org
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    kernel/rtmutex.c | 6 +++---
    1 files changed, 3 insertions(+), 3 deletions(-)

    diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
    index 789744a..a02fbd9 100644
    --- a/kernel/rtmutex.c
    +++ b/kernel/rtmutex.c
    @@ -1365,14 +1365,14 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
    * PI_REQUEUE_INPROGRESS, so that if the task is waking up
    * it will know that we are in the process of requeuing it.
    */
    - raw_spin_lock(&task->pi_lock);
    + raw_spin_lock_irq(&task->pi_lock);
    if (task->pi_blocked_on) {
    - raw_spin_unlock(&task->pi_lock);
    + raw_spin_unlock_irq(&task->pi_lock);
    raw_spin_unlock(&lock->wait_lock);
    return -EAGAIN;
    }
    task->pi_blocked_on = PI_REQUEUE_INPROGRESS;
    - raw_spin_unlock(&task->pi_lock);
    + raw_spin_unlock_irq(&task->pi_lock);
    #endif

    ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
    --
    1.7.8.3



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